Heart functions are closely correlated not only with electrocardiogram waveforms (electrocardiograms) but also with bio-signals periodically changing due to motions of a heart such as pulses, blood pressures, and heart sounds, so that those bio-signals are used to perform a heart function test. The hear function test involves displaying section images of organs with an ultrasonic diagnostic apparatus over several cycles of the periodically changing bio-signal and computing measurement data representing the hear functions such as the bloodstream state, bloodstream rate, annulus rate, atrium volume, and heart wall motions.
It is presumed that the heart function test should desirably be performed with a plurality of cycles of the bio-signal remaining stable. Thus, ultrasonic measurement data including ultrasonic image data is acquired in association with the changes of the bio-signal and is once stored in a storage section such as a cine memory. Then, for example, a tester retrieves the cycle in which the bio-signal is stable while seeing the bio-signal and the reproduced image of the ultrasonic measurement data, and sets the retrieved cycle to a test period to perform the heart function measurement.
In a case with arrhythmia having unstable pulses, the electrocardiogram waveforms stored in the cine memory are reproduced, and the tester advances frames one by one using an input unit to retrieve the period with stable pulses while seeing the electrocardiogram waveforms.
In Non-Patent document 1, time intervals (R-R time) between two adjacent R waves from one R wave (heart beat) to the next R wave are sequentially measured on the basis of electrocardiogram waveforms, and a tester manually retrieves with an input unit, as a conforming period, the period in which the ratio between two adjacent R-R times is approximately one, and specifies the R-R time immediately after the conforming period as a test period. The hear function measurement is performed in the test period. The measurement is shown to be valid as the measurement value in the case with arrhythmia.
According to the method described in Non-Patent document 1, however, the retrieval of the conforming period requires the tester to watch the displayed image to determine whether or not the ratio between the two adjacent R-R times falls within the allowable range to retrieve the conforming period while he manually reproduces the bio-signal with the input unit. This causes time and effort and a burden on the tester, and in addition, when the tester erroneously retrieves the conforming period, he may retrieve an inappropriate test period as a result.
On the other hand, Patent Document 1 has proposed that the waveforms from a certain R wave to the second earlier R wave are taken on the basis of the history of electrocardiogram waveforms, the difference between the two R-R times included therein is calculated, and when the time difference is equal to or lower than a preset threshold value, that period is evaluated as a conforming period in which pulses are stable.